phynexis-deps/lapack
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
Files
introduce-cpp
lapack/TESTING/LIN/csbmv.f
T
Julie e18d437924 Making LAPACK's code eternal... no more version and date in source files. 
GitHub is now enabling us to track accurately version and date.
No need for this anymore.
2021-03-25 10:16:58 -07:00

346 lines
10 KiB
FortranFixed
Raw Permalink Blame History

*> \brief \b CSBMV
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE CSBMV( UPLO, N, K, ALPHA, A, LDA, X, INCX, BETA, Y,
* INCY )
*
* .. Scalar Arguments ..
* CHARACTER UPLO
* INTEGER INCX, INCY, K, LDA, N
* COMPLEX ALPHA, BETA
* ..
* .. Array Arguments ..
* COMPLEX A( LDA, * ), X( * ), Y( * )
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> CSBMV performs the matrix-vector operation
*>
*> y := alpha*A*x + beta*y,
*>
*> where alpha and beta are scalars, x and y are n element vectors and
*> A is an n by n symmetric band matrix, with k super-diagonals.
*> \endverbatim
*
* Arguments:
* ==========
*
*> \verbatim
*> UPLO - CHARACTER*1
*> On entry, UPLO specifies whether the upper or lower
*> triangular part of the band matrix A is being supplied as
*> follows:
*>
*> UPLO = 'U' or 'u' The upper triangular part of A is
*> being supplied.
*>
*> UPLO = 'L' or 'l' The lower triangular part of A is
*> being supplied.
*>
*> Unchanged on exit.
*>
*> N - INTEGER
*> On entry, N specifies the order of the matrix A.
*> N must be at least zero.
*> Unchanged on exit.
*>
*> K - INTEGER
*> On entry, K specifies the number of super-diagonals of the
*> matrix A. K must satisfy 0 .le. K.
*> Unchanged on exit.
*>
*> ALPHA - COMPLEX
*> On entry, ALPHA specifies the scalar alpha.
*> Unchanged on exit.
*>
*> A - COMPLEX array, dimension( LDA, N )
*> Before entry with UPLO = 'U' or 'u', the leading ( k + 1 )
*> by n part of the array A must contain the upper triangular
*> band part of the symmetric matrix, supplied column by
*> column, with the leading diagonal of the matrix in row
*> ( k + 1 ) of the array, the first super-diagonal starting at
*> position 2 in row k, and so on. The top left k by k triangle
*> of the array A is not referenced.
*> The following program segment will transfer the upper
*> triangular part of a symmetric band matrix from conventional
*> full matrix storage to band storage:
*>
*> DO 20, J = 1, N
*> M = K + 1 - J
*> DO 10, I = MAX( 1, J - K ), J
*> A( M + I, J ) = matrix( I, J )
*> 10 CONTINUE
*> 20 CONTINUE
*>
*> Before entry with UPLO = 'L' or 'l', the leading ( k + 1 )
*> by n part of the array A must contain the lower triangular
*> band part of the symmetric matrix, supplied column by
*> column, with the leading diagonal of the matrix in row 1 of
*> the array, the first sub-diagonal starting at position 1 in
*> row 2, and so on. The bottom right k by k triangle of the
*> array A is not referenced.
*> The following program segment will transfer the lower
*> triangular part of a symmetric band matrix from conventional
*> full matrix storage to band storage:
*>
*> DO 20, J = 1, N
*> M = 1 - J
*> DO 10, I = J, MIN( N, J + K )
*> A( M + I, J ) = matrix( I, J )
*> 10 CONTINUE
*> 20 CONTINUE
*>
*> Unchanged on exit.
*>
*> LDA - INTEGER
*> On entry, LDA specifies the first dimension of A as declared
*> in the calling (sub) program. LDA must be at least
*> ( k + 1 ).
*> Unchanged on exit.
*>
*> X - COMPLEX array, dimension at least
*> ( 1 + ( N - 1 )*abs( INCX ) ).
*> Before entry, the incremented array X must contain the
*> vector x.
*> Unchanged on exit.
*>
*> INCX - INTEGER
*> On entry, INCX specifies the increment for the elements of
*> X. INCX must not be zero.
*> Unchanged on exit.
*>
*> BETA - COMPLEX
*> On entry, BETA specifies the scalar beta.
*> Unchanged on exit.
*>
*> Y - COMPLEX array, dimension at least
*> ( 1 + ( N - 1 )*abs( INCY ) ).
*> Before entry, the incremented array Y must contain the
*> vector y. On exit, Y is overwritten by the updated vector y.
*>
*> INCY - INTEGER
*> On entry, INCY specifies the increment for the elements of
*> Y. INCY must not be zero.
*> Unchanged on exit.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup complex_lin
*
* =====================================================================
SUBROUTINE CSBMV( UPLO, N, K, ALPHA, A, LDA, X, INCX, BETA, Y,
$ INCY )
*
* -- LAPACK test routine --
* -- LAPACK is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
* .. Scalar Arguments ..
CHARACTER UPLO
INTEGER INCX, INCY, K, LDA, N
COMPLEX ALPHA, BETA
* ..
* .. Array Arguments ..
COMPLEX A( LDA, * ), X( * ), Y( * )
* ..
*
* =====================================================================
*
* .. Parameters ..
COMPLEX ONE
PARAMETER ( ONE = ( 1.0E+0, 0.0E+0 ) )
COMPLEX ZERO
PARAMETER ( ZERO = ( 0.0E+0, 0.0E+0 ) )
* ..
* .. Local Scalars ..
INTEGER I, INFO, IX, IY, J, JX, JY, KPLUS1, KX, KY, L
COMPLEX TEMP1, TEMP2
* ..
* .. External Functions ..
LOGICAL LSAME
EXTERNAL LSAME
* ..
* .. External Subroutines ..
EXTERNAL XERBLA
* ..
* .. Intrinsic Functions ..
INTRINSIC MAX, MIN
* ..
* .. Executable Statements ..
*
* Test the input parameters.
*
INFO = 0
IF( .NOT.LSAME( UPLO, 'U' ) .AND. .NOT.LSAME( UPLO, 'L' ) ) THEN
INFO = 1
ELSE IF( N.LT.0 ) THEN
INFO = 2
ELSE IF( K.LT.0 ) THEN
INFO = 3
ELSE IF( LDA.LT.( K+1 ) ) THEN
INFO = 6
ELSE IF( INCX.EQ.0 ) THEN
INFO = 8
ELSE IF( INCY.EQ.0 ) THEN
INFO = 11
END IF
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'CSBMV ', INFO )
RETURN
END IF
*
* Quick return if possible.
*
IF( ( N.EQ.0 ) .OR. ( ( ALPHA.EQ.ZERO ) .AND. ( BETA.EQ.ONE ) ) )
$ RETURN
*
* Set up the start points in X and Y.
*
IF( INCX.GT.0 ) THEN
KX = 1
ELSE
KX = 1 - ( N-1 )*INCX
END IF
IF( INCY.GT.0 ) THEN
KY = 1
ELSE
KY = 1 - ( N-1 )*INCY
END IF
*
* Start the operations. In this version the elements of the array A
* are accessed sequentially with one pass through A.
*
* First form y := beta*y.
*
IF( BETA.NE.ONE ) THEN
IF( INCY.EQ.1 ) THEN
IF( BETA.EQ.ZERO ) THEN
DO 10 I = 1, N
Y( I ) = ZERO
10 CONTINUE
ELSE
DO 20 I = 1, N
Y( I ) = BETA*Y( I )
20 CONTINUE
END IF
ELSE
IY = KY
IF( BETA.EQ.ZERO ) THEN
DO 30 I = 1, N
Y( IY ) = ZERO
IY = IY + INCY
30 CONTINUE
ELSE
DO 40 I = 1, N
Y( IY ) = BETA*Y( IY )
IY = IY + INCY
40 CONTINUE
END IF
END IF
END IF
IF( ALPHA.EQ.ZERO )
$ RETURN
IF( LSAME( UPLO, 'U' ) ) THEN
*
* Form y when upper triangle of A is stored.
*
KPLUS1 = K + 1
IF( ( INCX.EQ.1 ) .AND. ( INCY.EQ.1 ) ) THEN
DO 60 J = 1, N
TEMP1 = ALPHA*X( J )
TEMP2 = ZERO
L = KPLUS1 - J
DO 50 I = MAX( 1, J-K ), J - 1
Y( I ) = Y( I ) + TEMP1*A( L+I, J )
TEMP2 = TEMP2 + A( L+I, J )*X( I )
50 CONTINUE
Y( J ) = Y( J ) + TEMP1*A( KPLUS1, J ) + ALPHA*TEMP2
60 CONTINUE
ELSE
JX = KX
JY = KY
DO 80 J = 1, N
TEMP1 = ALPHA*X( JX )
TEMP2 = ZERO
IX = KX
IY = KY
L = KPLUS1 - J
DO 70 I = MAX( 1, J-K ), J - 1
Y( IY ) = Y( IY ) + TEMP1*A( L+I, J )
TEMP2 = TEMP2 + A( L+I, J )*X( IX )
IX = IX + INCX
IY = IY + INCY
70 CONTINUE
Y( JY ) = Y( JY ) + TEMP1*A( KPLUS1, J ) + ALPHA*TEMP2
JX = JX + INCX
JY = JY + INCY
IF( J.GT.K ) THEN
KX = KX + INCX
KY = KY + INCY
END IF
80 CONTINUE
END IF
ELSE
*
* Form y when lower triangle of A is stored.
*
IF( ( INCX.EQ.1 ) .AND. ( INCY.EQ.1 ) ) THEN
DO 100 J = 1, N
TEMP1 = ALPHA*X( J )
TEMP2 = ZERO
Y( J ) = Y( J ) + TEMP1*A( 1, J )
L = 1 - J
DO 90 I = J + 1, MIN( N, J+K )
Y( I ) = Y( I ) + TEMP1*A( L+I, J )
TEMP2 = TEMP2 + A( L+I, J )*X( I )
90 CONTINUE
Y( J ) = Y( J ) + ALPHA*TEMP2
100 CONTINUE
ELSE
JX = KX
JY = KY
DO 120 J = 1, N
TEMP1 = ALPHA*X( JX )
TEMP2 = ZERO
Y( JY ) = Y( JY ) + TEMP1*A( 1, J )
L = 1 - J
IX = JX
IY = JY
DO 110 I = J + 1, MIN( N, J+K )
IX = IX + INCX
IY = IY + INCY
Y( IY ) = Y( IY ) + TEMP1*A( L+I, J )
TEMP2 = TEMP2 + A( L+I, J )*X( IX )
110 CONTINUE
Y( JY ) = Y( JY ) + ALPHA*TEMP2
JX = JX + INCX
JY = JY + INCY
120 CONTINUE
END IF
END IF
*
RETURN
*
* End of CSBMV
*
END
Reference in New Issue View Git Blame Copy Permalink